大约有 16,000 项符合查询结果（耗时：0.0210秒） [XML]
Are there disadvantages to using a generic varchar(255) for all text-based fields?
... copied from the storage engine layer to the SQL layer, VARCHAR fields are converted to CHAR to gain the advantage of working with fixed-width rows. So the strings in memory become padded out to the maximum length of your declared VARCHAR column.
When your query implicitly generates a temporary ta...
How can I add (simple) tracing in C#? [closed]
I want to introduce some tracing to a C# application I am writing. Sadly, I can never really remember how it works and would like a tutorial with reference qualities to check up on every now and then. It should include:
...
What is the opposite of 'parse'? [closed]
I have a function, parseQuery, that parses a SQL query into an abstract representation of that query.
33 Answers
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How to get the concrete class name as a string? [duplicate]
...classes themselves as keys, not necessarily the classnames
typefunc={
int:lambda x: x*2,
str:lambda s:'(*(%s)*)'%s
}
def transform (param):
print typefunc[type(param)](param)
transform (1)
>>> 2
transform ("hi")
>>> (*(hi)*)
here typefunc is a dict that maps a func...
Sorting dictionary keys in python [duplicate]
I have a dict where each key references an int value. What's the best way to sort the keys into a list depending on the values?
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How do I forward declare an inner class? [duplicate]
...not make sense in this context and is doubtful to be accurate. The whole point of a forward declaration is that you are telling the compiler that there is a class (or in this case, an inner class). That specific statement of yours would be just as true of normal classes and would mean you can't forw...
Are nested transactions allowed in MySQL?
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InnoDB supports SAVEPOINTS.
You can do the following:
CREATE TABLE t_test (id INT NOT NULL PRIMARY KEY) ENGINE=InnoDB;
START TRANSACTION;
INSERT
INTO t_test
VALUES (1);
SELECT *
FROM t_test;
id
---
1
SAVEPOINT tran2;
INSERT
INTO...
Iterating over all the keys of a map
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https://play.golang.org/p/JGZ7mN0-U-
for k, v := range m {
fmt.Printf("key[%s] value[%s]\n", k, v)
}
or
for k := range m {
fmt.Printf("key[%s] value[%s]\n", k, m[k])
}
Go language specs for for statements specifies that the first value is the key, the second variable is the value,...
get string value from UISegmentedControl
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[segmentedControl titleForSegmentAtIndex:int];
For the current selected index
[segmentedControl titleForSegmentAtIndex:[segmentedControl selectedSegmentIndex]];
share
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python ? (conditional/ternary) operator for assignments [duplicate]
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@karadoc right point but bad example&no explanation for the second example: for beginners: if "something" is considered empty/falsy => it is evaluated to False => so you will NEVER get values like 0 (int zero), ""(empty string), [] ...